Allowing higher density would reduce the education gap between rich and poor significantly, the study concludes.

The findings deal a blow to the contentions of commentators Wendell Cox and Joel Kotkin, well-distributed of late on the editorial pages and online Wall Street Journal. Cox and Kotkin argue that planners' attempts to promote density in California are driving housing costs up and forcing people out of the state.

Others have argued that California land use regulations are arguably too strict in many ways, but criticisms of higher density in this regard are 180 degrees wrong.

This Brookings study, by Jonathan Rothwell, finds that zoning restrictions, particularly limits on density, have adverse economic and social impacts. Conservative Harvard economist Edward Glaeser argued similar points in his 2011 book Triumph of the City.

Rothwell finds that zoning restrictions are correlated to more extreme differences in housing cost and greater educational gaps between rich and poor in metropolitan areas.

Below is a summary of the findings from the report, and "exclusionary zoning" largely corresponds to the degree to which density is discouraged through minimum lot size, restrictions on multifamily units, and other means. The study looked at national and metropolitan data on public school populations for 84,077 schools in 2010 and 2011:

• Nationwide, the average low-income student attends a school that scores at the 42nd percentile on state exams, while the average middle/high-income student attends a school that scores at the 61st percentile on state exams. This school test-score gap is even wider between black and Latino students and white students. There is increasingly strong evidence—from this report and other studies—that low-income students benefit from attending higher-scoring schools.

• Northeastern metro areas with relatively high levels of economic segregation exhibit the highest school test-score gaps between low-income students and other students. Controlling for regional factors such as size, income inequality, and racial/ethnic diversity associated with school test-score gaps, Southern metro areas such as Washington and Raleigh, and Western metros like Portland and Seattle, stand out for having smaller-than-expected test-score gaps between schools attended by low-income and middle/high-income students.

• Across the 100 largest metropolitan areas, housing costs an average of 2.4 times as much, or nearly $11,000 more per year, near a high-scoring public school than near a low-scoring public school. This housing cost gap reflects that home values are $205,000 higher on average in the neighborhoods of high-scoring versus low-scoring schools. Near high-scoring schools, typical homes have 1.5 additional rooms and the share of housing units that are rented is roughly 30 percentage points lower than in neighborhoods near low-scoring schools.

• Large metro areas with the least restrictive zoning have housing cost gaps that are 40 to 63 percentage points lower than metro areas with the most exclusionary zoning. Eliminating exclusionary zoning in a metro area would, by reducing its housing cost gap, lower its school test-score gap by an estimated 4 to 7 percentiles—a significant share of the observed gap between schools serving the average low-income versus middle/higher-income student.

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